Friction

The friction keeps the device in your hand, as long as you keep your fingers closed. If the grip is loose enought, the device slips out of the grip.

With friction, there comes the following redundancy (see chapter "Redundancy) :

(1) The usual advice is, to release the device at the right time as suddenly as possible. "As if it were a burning coal all of a sudden", as John Bailey sais.

(2) But what you will sometimes hear as well is, to let the device slip out of the hand "slowly" by its own impuls.

Our judgement is, to follow John Baileys advice. But no movement can be done in zero time. So there remains always a small component of slipping. Even if the slipping is wantet to be reduced to zero, it is worth to be watched. If I cannot exclude something, then I try to cultivate it.